In general, a washing machine is classified into a pulsator type washing machine, a drum type washing machine and an agitator type washing machine. The pulsator type washing machine washes laundry using the friction force generated between water current and the laundry by rotating a pulsator, the drum type washing machine washes laundry using drop of the laundry as well as friction force, and the agitator type washing machine washes the laundry using rotatory force by rotating an agitator mounted perpendicularly.
In recent days, it is thus seen that there has been provided a washing machine using steam especially a drum type washing machine which is adapted to use steam for enhancing washing efficiency as well as economizing in water and electric power. Also, wrinkles and bad smell of laundry may be prevented.
Referring to FIGS. 1 and 2, a drum type washing machine, as an example of a washing machine using steam, will be described.
A drum type washing machine includes a cabinet 110 defining an exterior thereof, a tub 120 vertically suspended within the cabinet 110 for holding washing water, a drum 130 rotatably mounted within the tub 120, a driving part 100 for driving the drum 130. A laundry introduction opening 112 is provided in front of the cabinet 110 for loading/unloading laundry, with being in communication with an inside of the drum 130. A door 140 is coupled to the laundry introduction opening 112.
A detergent box 114 and a steam generator 50 is provided in an upper portion of the drum type washing machine. Also, a water supply valve 15: 15a, 15b and 15c is provided in the upper portion of the drum-type washing machine, and is connected with a water pipe (not shown) outside. Commonly, a cold water pipe 113 and a hot water pipe 113a are connected each between the detergent box 114 and the water supply valve 15a and 15b. A water supplying hose 113b is connected with a first side of the steam generator 50, and a steam supplying pipe 220 is connected to a second side thereof. The water supplying valve 15c allowing the water supplying hose 113b connected thereto is generally connected to hot water. Preferably, a first end of the steam supplying pipe is provided with a nozzle 230 for injecting steam into the drum without any difficulties.
As shown in FIGS. 2 and 3, a temperature sensor 150 is provided in the tub 120 for sensing the temperature of washing water within the tub 120 as well as the temperature of a heater for heating washing water supplied into the tub 120. Also, a circulation channel 170 and a circulation pump 160 may be provided for re-circulating the washing water of the tub 120 into the drum 130.
Referring to FIGS. 1, 4 and 5, a structure of the steam generator will be described.
The steam generator 50 includes a lower housing 51 for defining an exterior thereof as well as space to hold water, an upper housing 52 secured to an upper surface of the lower housing 51, and a heater 320 for heating the water held within the steam generator 50.
An inlet 52a connected to a water supplying hose 220 is formed at a first side of the upper housing 52 for drawing water into the steam generator 50, whereas an outlet 52b is formed at a second side thereof connected to the steam supplying pipe for supplying generated steam into the drum 120.
The heater 320 is provided in a downside of the lower housing 51, and heats water in a state of being completely sunk in water. For that, a water level sensor 300 is provided within the upper housing 52 for sensing a water level held in the upper housing 52. The water level sensor 300 senses the water level held within the steam generator for maintaining the appropriate amount of the water. That is, once the water level held within the steam generator 50 is lower than a preset value (a preset low water level), the water supplying valve 15c is opened for filling up water, whereas once the water level within the steam generator 50 reaches a preset value (a preset high water level), the water supplying valve 15c is closed to stop supplying water and the heater 320 is operated to generate steam. Also, a temperature sensor 57 is provided for sensing the temperature of water as well as steam heated by the heater 320. The temperature sensor 57 senses the temperature of steam generated in the steam generator 50. Hence, once the temperature is higher than a preset value, power of the heater 320 is shut off to prevent overheating.
The water level sensor 300 includes a receptacle housing 334 for securing the water level sensor to the steam generator 50, an electrode 331, 332 and 333 each provided in a lower portion of the receptacle housing 334 for sensing the water level within the steam generator 50. The electrode is includes a common electrode 331, a long electrode 332 for sensing a low water lever and a short electrode 333 for sensing a high water level. Each electrode 331, 332 and 333 is provided at a predetermined height from a downside of the lower housing 51 for sensing a water level held within the steam generator 50.
Referring to FIG. 6, a related art method for controlling a conventional drum type washing machine will be described.
In general, there may be included a washing, a rinsing and a dehydrating stroke in a washing process of the drum type washing machine. The washing and rinsing stroke includes a water-supplying stroke. A soaking stroke may be further included in the washing process. Generally, in case that steam is used in a drum type washing machine, steam is injected into a drum in the washing and/or rinsing stroke by means of a predetermined method. Of course, a steam generator is operated for injecting steam. There are various steam injecting methods, and the description thereof will be omitted.
There may be also a hand-operated course for selectively performing a washing, rinsing and dehydrating stroke, and an automatic course for automatically performing each stroke. In case of the automatic course, each condition of the processes, such as a water level and numbers of rinsing, is preset based on a kind of the laundry and a degree of contamination. Also, a steam course may be selected in the automatic and hand-operated course.
As a first embodiment of the related art method for controlling the washing machine, a washing course process selecting a steam stroke, in other words, a steam washing will be described. The following description is only an embodiment, and alternatively other methods for controlling a washing machine are also possible.
First, once power is supplied (S401) and laundry introduction is sensed (S402), water is supplied to a steam generator and a tub S407 and (S403). Hence, the steam generator and the tub determine whether each water level thereof reaches a preset water level by using output values of each water level sensor provided in the steam generator and the tub.
That is, based on the output values sensed by a water level sensor (see FIG. 4) of the steam generator (S408), it is determined whether the water level of the steam generator reaches a preset water level, in other words, a preset high water level (S409). In case that the water level reaches a preset high water level, a water supply valve connected with the steam generator (see FIG. 1) is closed (S410).
Respectively, based on the output values sensed by a water level sensor of the (S404), it is determined whether the water level of the steam generator reaches the preset water level, in other words, a preset high water level (S409). In case that the water level reaches the preset high water level, a water supply valve connected with the steam generator (see FIG. 1) is closed (S410). Commonly, the water supply valve of the steam generator is closed first, and then the water supply valve of the tub is closed.
Once supplying water into the steam generator and the tub is completed, a heater of the steam generator is operated for generating steam (S412). Also, a circulation pump and a drum motor are on/off for loading the laundry uniformly and distributing detergent uniformly (S411). Hence, while supplying steam into a drum a step of determining whether water is re-supplied based on result of water levels each sensed by the steam generator and the tub. Thus, in case re-supplying water is determined as necessary, water is re-supplied (S415).
On the other hand, it is identified if the temperature of washing water in the drum, that is, the temperature of washing water in the tub reaches a preset high water temperature (S416). Hence, once the temperature is identified to reach the preset high water temperature, the heater of the steam generator is stopped. Of course, the heater of the tub is also stopped. After the above process is completed, the next process will start.